Construction, earthmoving, and agricultural type work vehicles are often equipped with endless self-laying track chain assemblies for support and propulsion of the vehicle. Such prior art track type vehicles, utilizing metal track chain assemblies, are generally low speed vehicles and work in environments not requiring relatively high ground clearance beneath the vehicle. More recently, work vehicles having endless, inextensible elastomeric track belts have been employed to perform work tasks previously accomplished by metal track equipped vehicles. The elastomeric track belt vehicles have many advantages over metal track vehicles and also over wheel type vehicles. Some of these advantages include less weight and maintenance, lower soil compaction, and the ability to travel on improved roadways.
One type of belted vehicle is disclosed in U.S. Pat. No. 4,817,746 issued to R. J. Purcell et al. on Apr. 4, 1989. In this patent, each of the endless elastomeric belts is driven by a pair of elevated drive wheels and is guided and supported by a pair of large diameter idler wheels and a plurality of smaller diameter roller assemblies. The idler wheels and roller assemblies are supported and suspended by a plurality of links, levers, and fluid cylinders. This large number of components in the undercarriage and suspension adds complexity, weight, and cost to the vehicle.
Another type of belted vehicle having a track roller frame assembly is disclosed in U.S. Pat. No. 4,836,318 issued to A. J. Tonsor et al. on June 6, 1989. This patent discloses a vehicle having a track roller frame which is connected to the front of the vehicle by a pivot joint, and is connected to the rear of the vehicle by a collar which extends between the two drive wheels. The track roller frame also has an inside support device which connects the roller frame to the vehicle on the inside of the drive wheels. Although this type of suspension and track roller frame would appear to function satisfactorily for this particular type of vehicle, it is rather complex and limits the ground clearance under the vehicle. The roller frame supports between the drive wheels and to the inside of the drive wheels would also tend to collect dirt and debris.
The present invention is directed toward overcoming one or more of the problems as set forth above.